Scene 4 is a comic scene offering a parody by providing a mocking imitation of the preceding serious scene (this scene mocks Scene 3, where Faustus wants to sell his soul for 24 years, whilst Scene 4, a clown wants to become a servant for 7 years)
Scene 4 serves to ridicule the presumed greatness of Faustus's achievements as he masters black magic at the price of his soul (by using the clown becoming a servant for 7 years)
In Scene 4, Wagner uses terrifying tactics and bribery to persuade the Clown, so Wagner now assumes a superior attitude and talks down to the clown, again recalling Faustus's arrogance and sense of entitled superiority